The present invention relates in general to gas leak detectors, and, in particular to a water-sensitive cutoff valve that automatically closes a path to a gas indicator upon sensing the presence of water to protect the indicator.
Handheld gas leak detectors or gas indicators are used to detect leaks from gas mains and the like. Water can damage the gas indicator. Typically, a probe on a flexible line to the gas indicator is used to get access to the zone being tested. Water can be drawn up to the gas indicator through the probe and cause damage.
It is highly desirable, then, to provide some means to prevent water from entering the gas indicator and damaging that indicator.
Water-soluble devices have been used as safeties to close a passage when water is present, but these devices are awkward to use and arm. U.S. Pat. No. 3,472,253 to Herscher et al discloses a water detector and valve shutoff that uses a spacing element loaded in compression by a valve element. The element fails when soaked in water. A nut must be removed and an entire assembly broken down to rearm the device. U.S. Pat. No. 2,798,503 to Carver et al discloses a tension loaded water-soluble link only as a safety shutoff for hot water heaters. The safety is remote from the valve.
U.S. Pat. No. 4,294,276 to Loren C. Harrison discloses a water-sensitive probe valve that houses a normally open valve mechanism in a barrel and a cap. The Harrison device is an improvement over those just discussed. The valve is held open by a water-soluble link secured between anchors, one on the valve element and one on a statinary part of the probe. Water weakens the band and it fails, closing the valve element and protecting the gas indicator. Access to the band for rearming is easy; the cap is merely taken off the barrel. Rearming is easy because there is a lock that keeps the valve open. It is sometimes preferred to have the water-sensitive shutoff valve out of the way of the gas probe, mounted to the gas detector, for example. It is advantageous, of course, to have the shutoff valve of simple construction, reliable in performance, and easily serviced and rearmed.